In internal combustion engines it has heretofore been suggested that operation of the engine from the standpoint of smoothness of operation and reduction in contaminants and impurities can be improved by utilizing a throttle positioning assembly which functions to maintain the throttle at a high idle position when it is released suddenly at a high vehicle speed and to permit the throttle to move to a throttle-closed position when the engine approaches normal idle rpm.
Such a throttle control assembly generally comprises a housing with a diaphragm therein separating the housing into a first and second chamber, the second chamber being connected to the vacuum created by engine operation through an intermediate control valve. A plunger or stem is usually connected to the diaphragm and extends through one wall of the housing into contact with the throttle stop when the throttle is closed and the positioner is energized. A spring normally urges the diaphragm and in turn the plunger against the action of the vacuum. The plunger is usually fastened to the diaphragm by rivets or other means and it has been found that adjustment of the plunger often causes the connection to the diaphragm to be torn or weakened. In an effort to improve this, it has heretofore been suggested that a rectangular or hexagonal portion be extending through a corresponding non-cylindrical hole extending through one wall of the housing to resist rotation of the plunger relative to the diaphragm. Such a construction has provided for improved operation. However, penetration of the diaphragm still was a source of potential leaks. In a further effort to improve the construction, it has been suggested that the plunger be attached to the diaphragm in a manner such that the plunger penetrates the diaphragm and that the plunger have a square cross section extending through the wall of the housing. This has produced improved construction, but there has been still a tendency to bind as the plunger moves back and forth within the housing. Such a throttle control assembly is shown, for example, in U.S. Pat. No. 3,618,582.
This invention is intended to provide a throttle control assembly which obviates the disadvantages achieved by prior throttle control assemblies.